How is Autism Diagnosed?

Presently, there is no definitive diagnostic method to screen for Autism Spectrum Disorder (ASD). Though there are a number of specific genetic markers associated with autism, such as the one that causes Fragile-X Syndrome, no single gene or set of genes have been identified that are consistently present in individuals with ASD.

In the United States, ASD is primarily diagnosed in early childhood, through developmental monitoring, screening, and evaluation performed as a part of standard wellness checkups. These checks can often identify cases of autism labelled as 'severe' in children by age 3, when significant developmental differences may be easily identified.

Once a child enters the education system, where educators and staff can observe the child for extended periods of time, they may be referred to a child psychologist or psychiatrist for evaluation and diagnosis. The evaluation may be performed through questioning, observation, and/or testing, primarily in an attempt to identify any common features of autism as defined by relevant diagnostic manuals.

There are no standardized tests to identify autism post adolescence, leading to a patchwork of methodology decided on by individual providers. Some may use questioning alone, some may utilize the same tests given to children, others may use a variety of resources.